Dr. Pittas and his team first began researching the effects of vitamin D supplementation on reducing diabetes risk in 2002. Since then, Dr. Pittas’ studies have identified an association between higher levels of vitamin D in the blood and a lower future risk of developing type 2 diabetes in people at the highest risk for the metabolic disorder. In addition, his investigations have shown that vitamin D supplementation may boost the body’s insulin production and processing. Now, after more than a decade dedicated to this research, Dr. Pittas’ group recently received a National Institutes of Health grant of more than $40 million over five years to fully fund the Vitamin D and Type 2 diabetes (D2d) study, a multi-centered, randomized clinical trial to put his hypothesis to its ultimate test.

“Vitamin D does look promising for type 2 diabetes in early studies; however, we simply do not know whether taking high doses of vitamin D on a long-term basis is of any benefit or even safe. We need to be cautious before adopting any intervention, especially of a nutrient, that looks very promising in early studies before rigorous testing is done,” says Dr. Pittas. “It is well known that leading an active lifestyle with exercise and a healthy diet lowers the risk of diabetes. But as the number of people with diabetes continues to increase, we need to identify new methods that are safe, effective and easily applied to prevent new diabetes cases.”

Commonly synthesized through sunlight exposure and found in many foods such as dairy products and seafood, vitamin D also can be easily obtained at any pharmacy or supermarket. Sales of vitamin D supplements in the United States have skyrocketed to $425 million annually, making it one of the top selling supplements in the country and one of the most talked about topics in health and medicine.

“While there is a lot of hype about vitamin D and its health benefits, there is not yet any conclusive evidence from long-term clinical trials to support a recommendation for or against vitamin D supplementation for diabetes prevention,” cautioned Dr. Pittas.

The D2d study, which is coordinated out of the Division of Endocrinology at Tufts Medical Center, is the first of its kind to specifically examine whether vitamin D has an effect on prevention of type 2 diabetes. About 2,500 people at high risk for diabetes will participate in the D2d study, which is being conducted at 20 medical centers in 17 different states across the country. Study participants will receive either vitamin D supplementation or placebo, and will be followed for development of diabetes for approximately four years. Results are expected in 2018.

“At the end of the five years, the goal is to have conclusive evidence as to whether Vitamin D supplementation lowers the risk of diabetes,” says Dr. Pittas. “Positive results could have a large impact on the quality of life for millions of people who are at risk for diabetes.”